Longitudinal trajectories of social isolation and loneliness across the lifespan during the COVID-19 pandemic in South Korea.

During the prolonged Coronavirus Disease 2019 pandemic persisting through to 2023, social isolation became a major public health concern. Its impacts varied across age groups, but empirical evidence on longitudinal trajectories of social isolation in South Korea remains limited. Thus, this study examined social isolation and loneliness trajectories in South Korea using longitudinal data from three waves (2021-2023) involving 2395 participants aged 15-79. Over that three-year period, social isolation increased steadily. Risk was elevated among middle-aged and older adults, men, those with lower educational attainment, lower income, and more severe depressive symptoms, and residents of urban areas. Rates of increased social isolation demonstrated a nonsignificant difference across age groups. By contrast, loneliness remained stable overall but declined among people in their 40 s, 50 s, and 60 s. Higher loneliness at baseline was associated with middle-age and older age, higher depression and anxiety, lower education and income, and urban residence. Depression predicted both social isolation and loneliness, whereas anxiety was associated only with loneliness. These findings highlight a clear divergence between objective social isolation and subjective loneliness, underscoring the need for age-specific and tailored interventions to effectively address each outcome.